Study On Zeta Potential Measurement Based On Phase Analysis Light Scattering

Particle’s Zeta potential is an important characterization parameter of the stability of colloidal system.The larger the particle’s Zeta potential,the more stable the colloid system,otherwise,the colloid system is more unstable.Therefore,we can judge the stability of the colloidal system by measuring the particle’s Zeta potential.We usually use the method of laser Doppler electrophoresis to measure the particle’s Zeta potential.However,the resolution of traditional laser Doppler electrophoresis technology is poor.When the value of particle electrophoretic mobility is small,In order to produce enough Doppler frequency shifts,we usually enhance the electric strength.Nevertheless,the enhanced electric strength leads to excessive joule heating and other undesirable effects,which seriously affects the accuracy of particle’s Zeta potential.Phase analysis light scattering is a kind of new technique for measuring the particle’s Zeta potential,which is based on the classical laser Doppler electrophoresis,but the sensitivity of phase analysis light scattering technology is at least two orders of magnitude higher than that of the laser Doppler electrophoresis technology.So it is not necessary to use the high electric field to measure the small mobility.This new technique has vast application prospect.So this paper research on Zeta potential measurement based on phase analysis light scattering,the main researches are as follows.1.Researched the relationship between particle’s Zeta potential and its electrophoretic mobility based on the model of Gouy-Chapman-Stern double layer.Discussed the influence of the factors such as particle radius,thickness of double layer,electrolyte solution,etc.on the ratio of Zeta potential to electrophoretic mobility.Obtained the accuracy f(ka)by using the least-squares algorithm.Provided a method for determiningthe ratio of particle radius to double layer thickness.2.Analyzed the limitation of the laser Doppler electrophoresis technology.Studied the relationship between the phase of scattering light and the electrophoretic mobility based on the principle of phase analysis light scattering,deduced the amplitude weighted phase difference function as well.Proposed the method for detecting the phase of scattered light.Extracted the amplitude and phase of the scattered light signal by the digital phase-locked amplifier with software programming.3.Simplified the optical path of reference beam,and put forward to the idea of beam alignment and adjustment.Designed the electric field drive circuit,provided the high voltage output by an adjustable precision dc high voltage module.Monitored electrode voltage and current in real-time.Improved the sample cell,designed a composite sample cell,which can ensure the heat dissipation speed of the sample and constant temperature performance in the measurement process.The experimental setup of particle’s Zeta potential measurement system based on phase analysis light scattering principle and the acquisition of light scattering data are completed.4.Calculated the Zeta potential by applying the method of electrophoresis light scattering and phase analysis light scattering respectively.The experimental result suggested that the higher resolution of measured electrophoretic mobility and the better values of Zeta potential obtained by phase analysis light scattering method.